Tanjiro and Nezuko went up to soak in the hotsprings, it was late night so Nezuko wouldn't get burned by the sun.

When they got to hotsprings they saw you, Tanjiro didn't smell you though so that was a bit strange. He guessed you were just a strong demon slayer that didn't really give off a scent. He tried getting a look at your face to see if he recognized you, but your back was turned to them and he couldn't see anything but your back and hair. Either you didn't notice them, or were just ignoring them.